Irradiation Cycles Research Articles

Evaluation and SNP typing of DNA from ultraviolet-irradiated human bloodstains using TaqMan assay

When detecting DNA profiles from forensic materials, it is pivotal to know the extent of degradation and which DNA marker can be genotyped. Ultraviolet (UV) is one of the common external factors that causes DNA damage, through which, an attempt to reveal cardinal genetic information can be made. In this study, after irradiation with three different UV wavelengths, UV-damaged DNA in the bloodstains was analyzed with long and short TaqMan assays using real-time PCR. In addition, both short tandem repeat (STR) profiles and single nucleotide polymorphisms (SNPs) from the damaged DNA at different stages of UV exposure were also assessed. With increasing in UV irradiation cycles, there was a delay of the amplification curves accompanied with a decrease in the DNA amounts collected. Despite the amplification of STR genotype was not altered after 75 cycles of UVC irradiation, all 12 SNP loci could still be detected. Furthermore, a short-assay line was detected in the absence of an amplification of the evaluation curve. The results indicate that, although the DNA template might not be useful and suitable for analysis of STR profile, this approach is of some values in detecting SNPs.

Effects of the key parameters of TRISO particle buffer layer on in-pile thermo-mechanical behavior in FCM fuel pellets

TRISO particle buffer layer is a critical functional part in FCM fuels. A skeleton stress model for buffer layer is proposed, dependent on the current porosity, the maximum macroscale tensile stress and the pore pressure, which is incorporated into the self-developed code of Thermo-mechanical Analysis of Inert Matrix Fuels (TMAIMF). Deeper insight is gained from the simulated thermo-mechanical variables in FCM fuel pellets, and the effects of buffer layer porosity and creep coefficient are investigated. This research indicates that (1) the macroscale maximum tensile stresses in the particle coating layers of buffer, IPyC and OPyC as well as the SiC matrix exhibit a significant decrease except those in SiC coating layers, when the initial porosity and creep coefficient of buffer layer increase; (2) with a rise of PyC creep coefficient, the maximum tensile stress of buffer layer skeleton and the buffer/IPyC interfacial tensile stresses will decrease heavily under irradiation conditions of LWRs, which gives an explanation for the no-cracking phenomenon in irradiated FCM surrogate pellets. Optimization of the microstructure of buffer layer and the creep performance of PyC materials might make the integrity and high heat transfer capability of FCM fuels maintained during a long irradiation cycle in LWRs.

Spatial and temporal variations in near‐surface energy fluxes in an Alpine valley under synoptically undisturbed and clear‐sky conditions

AbstractDiurnal cycles of turbulent sensible and latent heat fluxes are typically closely related to the diurnal cycles of solar irradiation under synoptically undisturbed and clear‐sky conditions. In mountainous terrain, large variations can occur in the topographic and surface properties, which modify the local radiation budget and thus turbulent energy fluxes and the surface energy balance. Another characteristic of mountainous terrain is local, thermally driven circulation systems, such as the slope‐ and valley‐wind system, which can equally affect turbulent exchange. Observations of near‐surface radiative and turbulent fluxes are presented from six eddy‐covariance stations in an approximately east–west‐oriented major Alpine valley for undisturbed and clear‐sky conditions. Median diurnal cycles over the whole year are compared at the six sites and related to local terrain characteristics and the thermally driven wind systems. At a scale that is smaller than grid cells in current operational global forecast models, heat, moisture, and momentum fluxes show a large spatial variability in the magnitudes and their diurnal cycles. Lowest heat fluxes are observed on the north‐facing sidewall, where solar irradiation and thus available energy are reduced compared with the valley floor and south‐facing sidewall. Differences in the land surface characteristics further affect the partitioning of the available energy into sensible and latent heat fluxes. The median sensible heat flux reaches its daily peak already before solar noon at several sites, which appears to be related to the transition from down‐valley to up‐valley winds. In contrast to flat and homogeneous terrain, horizontal heat fluxes and lateral momentum fluxes can reach magnitudes that are similar to the magnitudes of vertical heat fluxes and longitudinal momentum fluxes, respectively.

High photoresponse of gold nanorods/zinc oxide photodetector using localised surface plasmon resonance

This study demonstrated the fabrication of the gold nanorods/zinc oxide photodetector (GNRs/ZnO PD) and PEGylated GNRs were decorated onto the planar ZnO device via the microchannel relocation process. Several properties, including the sensitivity, responsibility, external quantum efficiency (EQE) and on/off switching ratio, were characterised under the 365 nm of the UV irradiation. The GNRs/ZnO PD performed stable and reproducible photocurrent responses and a high on/off switching ratio under the UV irradiation cycles. The photocurrent and Ilight/Idark current ratio increased to approximately 9 times and 167, respectively. Furthermore, the UV responsibility was enhanced to 180 A/W and the EQE was also improved to 612. These performance enhancements are dominated by the localised surface plasmon resonance (LSPR) effect of decorated GNRs. PEGylated GNRs have longitudinal and transverse LSPR peaks around 510 nm and 696 nm, respectively. The LSPR effect of decorated GNRs assists to enhance the UV emission of the ZnO PD by 25 times.

Experiments and modelling of multiple sequential MeV ion irradiations and deuterium exposures in tungsten

Bulk tungsten samples were irradiated sequentially with 20 MeV tungsten ions and exposed to deuterium plasma. The experiments were performed in order to simulate the displacement damage that fusion neutrons will cause in a tungsten plasma-facing component of a future fusion device. To study the influence of the presence of hydrogen isotopes during the creation of displacement damage on the final defect density, tungsten irradiation and deuterium decoration cycles were performed up to three times. Deuterium depth profiling with 3He Nuclear Reaction Analysis and Thermal Desorption Spectroscopy showed that the deuterium concentration increased after each additional tungsten irradiation and deuterium exposure. After the third cycle, the deuterium concentration reached a maximum of 3.6 at.% at the given plasma exposure temperature of 370 K. We attribute this increase in retention to the stabilization of the displacement damage during the tungsten irradiation by the presence of deuterium. The experimental results were simulated using the MHIMS-R macroscopic rate-equation code, which was recently upgraded with a damage stabilization term to describe experiments where tungsten was irradiated with MeV tungsten ions and simultaneously exposed to low-energy deuterium ions. Using this novel model, it was possible to quantitatively describe also the present results for the sequential irradiation/exposure scheme, with model parameters that were congruent with parameters derived from the simultaneous experiment. Modelling shows that kinetic de-trapping of trapped deuterium takes place during irradiation However, it is not the dominant process that explains defect stabilization. In addition, the model facilitates the extrapolation of present experimental results to an even larger number of sequential tungsten irradiation and deuterium exposure cycles. The model predicts that after about five sequential irradiation and plasma exposure cycles, a stationary state is reached with an associated maximum trapped D concentration of 4.2 at.% for the given exposure temperature of 370 K.

N-cadherin upregulation mediates adaptive radioresistance in glioblastoma.

Glioblastoma (GBM) is composed of heterogeneous tumor cell populations, including those with stem cell properties, termed glioma stem cells (GSCs). GSCs are innately less radiation sensitive than the tumor bulk and are believed to drive GBM formation and recurrence after repeated irradiation. However, it is unclear how GSCs adapt to escape the toxicity of repeated irradiation used in clinical practice. To identify important mediators of adaptive radioresistance in GBM, we generated radioresistant human and mouse GSCs by exposing them to repeat cycles of irradiation. Surviving subpopulations acquired strong radioresistance in vivo, which was accompanied by a reduction in cell proliferation and an increase in cell-cell adhesion and N-cadherin expression. Increasing N-cadherin expression rendered parental GSCs radioresistant, reduced their proliferation, and increased their stemness and intercellular adhesive properties. Conversely, radioresistant GSCs lost their acquired phenotypes upon CRISPR/Cas9-mediated knockout of N-cadherin. Mechanistically, elevated N-cadherin expression resulted in the accumulation of β-catenin at the cell surface, which suppressed Wnt/β-catenin proliferative signaling, reduced neural differentiation, and protected against apoptosis through Clusterin secretion. N-cadherin upregulation was induced by radiation-induced IGF1 secretion, and the radiation resistance phenotype could be reverted with picropodophyllin, a clinically applicable blood-brain-barrier permeable IGF1 receptor inhibitor, supporting clinical translation.

Photocatalytic ZnO Foams for Micropollutant Degradation

AbstractPhotocatalytic foams can concomitantly overcome the disadvantages of slurry and immobilized photocatalysts in water treatment. However, foams have, so far, been restricted to nanoparticles grafting onto inert foam substrates, with the consequent risk of nanoparticle release into the environment. In this work, self‐supporting, highly porous photocatalytic zinc oxide (ZnO) foams are produced using a combination of liquid templating and sintering for the first time. Systematic changes in sintering times and temperature affect the foams’ morphology and structure, in turn controlling their photocatalytic activity and stability. Sintering at 900 °C and decreasing sintering times from 20 to 6 h lead to a doubling in surface‐area‐to‐volume ratio and a 30% increase in pore diameter, resulting in a near doubling of the overall quantum yield and degradation kinetics. However, photocorrosion and Zn leaching increase markedly for the shortest sintering time. Optimal sintering conditions at 900 °C for 12 h yield foams capable of effectively degrading the model micropollutant carbamazepine under UV irradiation with high stability, showing no performance decrease over five irradiation cycles corresponding to 20 h of use. This study paves the way to producing self‐supporting, highly stable photocatalytic foams for the removal of organic micropollutants in water treatment.

Release Analysis of Nano-Titanium Dioxide (TiO2) from Paint: An Accelerated Weathering Experiment

Engineered nanomaterials (ENM’s), particularly TiO2 nanoparticles are being incorporated on paints due to their capabilities to enhance optical properties and to scatter UV radiation, which eventually protects the paint from discoloration. In this study, the release of these nano-TiO2 from paint was investigated. Two (2) types of paint were used, one containing pigment- and nano-TiO2 (P1), while the other only contains pigment-TiO2 (P2). The paints were subjected to accelerated weathering wherein the paints were exposed to cycles of UV irradiation and water condensation. The SEM-EDX results showed the distribution of the pigment- and nano-TiO2 on the surface of P1 and P2, and the changes in the morphologies before and after weathering. The photomicrograph revealed the formation of cracks on the surface of P1 brought about by the photocatalytic degradation due to the presence of nano-TiO2. Leachate samples were also collected weekly in the duration of the weathering test and were analysed using ICP-OES. The presence of Ti, which can be correlated to the release TiO2, on the samples was detected. The release of Ti from P1 and P2 showed a decreasing trend throughout the weathering experiment, having the following initial amounts of release: 1.38 mg/L and 2.10 mg/L for P1 and P2, respectively. Moreover, a graphical release mechanism for the nano-TiO2 release was conceptualized based on the results of the study. In general, potential release of nano-TiO2 from paints could happen since these TiO2 nanoparticles serve as a photocatalyst in the paint degradation when exposed to prolonged weathering conditions.

An Exceptional Broad-Spectrum Nanobiocide for Multimodal and Synergistic Inactivation of Drug-Resistant Bacteria

An Exceptional Broad-Spectrum Nanobiocide for Multimodal and Synergistic Inactivation of Drug-Resistant Bacteria

Effect of intermittent irradiation and fluence-response of 222 nm ultraviolet light on SARS-CoV-2 contamination.

BackgroundThe effectiveness of 222 nm ultraviolet (UV) C light for disinfecting surfaces contaminated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported. The aim of this study was to evaluate the effect of the intermittent irradiation of 222 nm UVC on SARS-CoV-2 and the fluence-dependent effect of 222 nm UVC irradiation on SARS-CoV-2 inactivation.MethodsWe experimented with 5 min continuous and intermittent irradiation for 0.1, 0.05, 0.013, and 0.003 mW/cm2 of 222 nm UVC to evaluate the differences in the effect of the continuous and intermittent irradiation of 222 nm UVC on SARS-CoV-2 inactivation. For intermittent irradiation, we followed the on-off irradiation cycles with every 10-s irradiation followed by a 380-s interval. Thereafter, we evaluated the effects of 0.1, 0.013, and 0.003 mW/cm2 222 nm UVC irradiation on SARS-CoV-2 contamination at UV fluences of 1, 2, and 3 mJ/cm2 at each irradiance.ResultsAt each irradiance, no significant difference was observed in the log reduction of SARS-CoV-2 between continuous and intermittent irradiation. At each UV fluence, no significant difference was observed in the log reduction of SARS-CoV-2 among the three different irradiance levels.ConclusionThere was no significant difference between continuous and intermittent irradiation with 222 nm UVC with regards to SARS-CoV-2 inactivation. Moreover, 222 nm UVC inactivates SARS-CoV-2 in a fluence-dependent manner. The efficacy of 222-nm UVC irradiation in reducing the contamination of SARS-CoV-2 needs to be further evaluated in a real-world setting.

Effects of Radiation Intensity, Mineral Matrix, and Pre-Irradiation on the Bacterial Resistance to Gamma Irradiation under Low Temperature Conditions.

Ionizing radiation is one of the main factors limiting the survival of microorganisms in extraterrestrial conditions. The survivability of microorganisms under irradiation depends significantly on the conditions, in which the irradiation occurs. In particular, temperature, pressure, oxygen and water concentrations are of great influence. However, the influence of factors such as the radiation intensity (in low-temperature conditions) and the type of mineral matrix, in which microorganisms are located, has been practically unstudied. It has been shown that the radioresistance of bacteria can increase after their exposure to sublethal doses and subsequent repair of damage under favorable conditions, however, such studies are also few and the influence of other factors of extraterrestrial space (temperature, pressure) was not studied in them. The viability of bacteria Arthrobacter polychromogenes, Kocuria rosea and Xanthomonas sp. after irradiation with gamma radiation at a dose of 1 kGy under conditions of low pressure (1 Torr) and low temperature (−50 °C) at different radiation intensities (4 vs. 0.8 kGy/h) with immobilization of bacteria on various mineral matrices (montmorillonite vs. analogue of lunar dust) has been studied. Native, previously non-irradiated strains, and strains that were previously irradiated with gamma radiation and subjected to 10 passages of cultivation on solid media were irradiated. The number of survived cells was determined by culturing on a solid medium. It has been shown that the radioresistance of bacteria depends significantly on the type of mineral matrix, on which they are immobilized, wherein montmorillonite contributes to an increased survivability in comparison with a silicate matrix. Survivability of the studied bacteria was found to increase with decreasing radiation intensity, despite the impossibility of active reparation processes under experimental conditions. Considering the low intensity of radiation on various space objects in comparison with radiobiological experiments, this suggests a longer preservation of the viable microorganisms outside the Earth than is commonly believed. An increase in bacterial radioresistance was revealed even after one cycle of irradiation of the strains and their subsequent cultivation under favourable conditions. This indicates the possibility of hypothetical microorganisms on Mars increasing their radioresistance.

Effects of irradiation on mechanical properties of nuclear UO2 fuels evaluated by Vickers indentation at room temperature

Vickers indentation was used to evaluate the hardness and the apparent fracture toughness of unirradiated and irradiated UO2 fuels, with the objective to determine the effects of the irradiation on mechanical properties. Indentation tests were realized at room temperature on standard and doped UO2 fuels, irradiated in a pressurised water reactor up to a burnup of 81.6 GWd/tM. For the highest burnups, the fuels had restructured in a high burnup structure (HBS) on the periphery of the pellets.More than 100 valid impressions for the Vickers hardness determination were obtained on each fuel. The Vickers hardness of both UO2 increased with the local burnup, due to irradiation defects such as dislocations and fission products but decreased when the fuel restructured into the HBS.Valid crack patterns for the Vickers fracture toughness were only obtained for indentations inside the large grains of irradiated doped UO2 fuels or for both restructured fuels. The Vickers fracture toughness of the non-restructured doped UO2 was shown to increase quickly during the first irradiation cycle but was then constant with increasing local burnup. This increase of the apparent fracture toughness was mainly due to the decrease of the crack length from the corner of the indents, attributed to the interactions of the cracks with the defects such as bubbles or fission product precipitates and associated residual stresses. In the HBS, short cracks from the corner of the indents that followed grain boundaries of small grains led to high fracture toughness values. However, the use of the literature equations to calculate the apparent fracture toughness on porous samples such as HBS is questioned. All tests clearly illustrated the weakness of the grain boundaries in irradiated fuels.

CABRI test events monitoring through three measurement systems

The CABRI experimental pulse reactor, located at the Cadarache nuclear research center, southern France, is devoted to the study of Reactivity Initiated Accidents (RIA). When the thermal-hydraulic conditions representative of a pressurized water nuclear reactor are reached (mostly temperature, pressure and flowrate conditions), a fuel test rod is submitted to a power excursion, triggered by the specific 3He reactivity injection system, in order to simulate a control rod ejection accident. The experiment, managed by IRSN, aims at studying both the fuel and cladding behavior of the test rod placed into the center of the reactor during the power excursion. Several test rods pre-irradiated in pressurized nuclear power plants and with different characteristics (burn up, cladding material, fuel type, Zirconia thickness) are considered for the programs performed in the CABRI reactor. Physical phenomena occurring during the power transient are monitored by various measuring systems designed or operated by IRSN. Each system provides information linked with the different phases of the experiment. Three main measuring systems will be considered in this paper: • The test devices, a sample holder that is also implemented with almost fifty sensors used to monitor the environmental parameters in the test channel such as temperature and pressure, and to control the rod behavior during the test sequence; • The Hodoscope, an online fuel motion measurement system, which aims at analyzing the fuel motion deduced from the detection of fast neutrons emitted by the test rod, with a time step of 1ms during the transient; • The IRIS facility, conceived to perform X-ray radiography and tomography imaging before and after a power transient thanks to a linear electron accelerator, as well as quantitative gamma scanning analyses. During the experimental sequence, different events are recorded. This paper focuses on a cladding failure that occurred during the transient and that can be revealed by the three systems mentioned above. The test device instrumentation allows to determine the timing of the failure and to analyze its consequences in the vicinity of the test rod from a thermal and hydraulic point of view, while the hodoscope measures fuel elongation and relocation during the power excursion. The IRIS facility, then, helps to confirm the failure, its location and its extent. These three systems are complementary and they allow the analysis of the same event from different perspectives. Their combination will ease the interpretation of the events in the next steps for the test results analysis. The study case taken into account in this paper concerns nuclear fuel after three irradiation cycles in a commercial PWR.

Boost Chopper Behaviors in Solar Photovoltaic System

This paper investigates the behaviors of Boost DC Chopper used in Photovoltaic energy systems where the solar irradiation changes during the day time causing current and voltage changes. Varying the solar irradiation causes output chopper voltage changes in order to keep working at maximum extracted solar power. The chopper voltage changes leading to variable duty cycle operation of chopper switch and causes a significant change in switch losses in terms of the dissipated power. In addition to that the chopper behaviors are studied when the chopper voltage is boosting up to a predetermined reference value leading to a significant change in chopper current, voltage, duty cycle and occurred losses. A mathematical model for chopper performances and switch losses is derived, and a simulation model using Matlab/ Simulink platforms is conducted to follow the chopper behaviors. Simulation results for concreteSUNPOWER panel type SPR-315E-WHT-D with 315 Watts peak indicates that during the daylight time transistors are exposed to complicated changes in their current, voltage and dissipated power. Furthermore changing the output voltage according to load requirements causes heavy stress on the transistor in terms of current, oscillations and losses as well. Simulation results show that there are optimized values of irradiation, chopper voltage and duty cycle where the transistor losses are minimized. In addition to that, projecting the transistor losses over the daylight time at a given irradiation rate shows how these losses vary among the year, and the amount of energy dissipated across the main chopper switch which is around 2970 Whr/yr for the present case. Furthermore, the conducted simulation also shows the occurred in the transistor behaviors when solar irradiation changes, and can be serving for further studies.

The Use of Artificial Intelligence‐Based Optical Remote Sensing and Positioning Technology in Microelectronic Processing Technology

The purpose is to make defect detection in microelectronic processing technology fast, accurate, reliable, and efficient. A new optical remote sensing‐optical beam induced resistance change (ORS‐OBIRCH) target recognition and location defect detection method is proposed based on an artificial intelligence algorithm, optical remote sensing (ORS), and optical beam induced resistance change (OBIRCH) location technology using deep convolutional neural network. This method integrates the characteristics of high resolution and rich details of the image obtained by ORS technology and combines the advantages of photosensitive temperature characteristics in OBIRCH positioning technology. It can be adopted to identify, capture, and locate the defects of microdevices in the process of microelectronic processing. Simulation results show that this method can quickly reduce the detection range and locate defects accurately and efficiently. The experimental results reveal that the ORS‐OBIRCH target recognition defect location detection method can complete the dynamic synchronization of the IC detection system and obtain high‐quality images by changing the laser beam irradiation cycle. Moreover, it can analyze and process the detection results to quickly, accurately, and efficiently locate the defect location. Unlike the traditional detection methods, the success rate of detection has been greatly improved, which is about 95.8%, an increase of nearly 40%; the detection time has been reduced by more than half, from 5.5 days to 1.9 days, and the improvement rate has reached more than 65%. In a word, this method has good practical application value in the field of microelectronic processing.

Gold nanoclusters modified mesoporous silica coated gold nanorods: Enhanced photothermal properties and fluorescence imaging

Photothermal therapy (PTT) is a non-invasive therapy that is widely used in cancer treatment. Gold nanorods (AuNRs) are particularly suitable as a photothermal reagent due to their unique localized surface plasmon resonance (LSPR) properties. However, bare gold nanorods are not stable enough during radiation to collect enough energy to kill tumor cells. In addition, they showed some biologically toxic originated from the poor colloidal stability and surfactants cetyltrimethyl ammonium bromide (CTAB), making it difficult to apply them directly to clinical research. To solve these problems, a novel nanocomposite was structured by coating silica shell and gold nanocluster on the outer layer of the gold nanorod (AuNRs@SiO2@AuNCs). Compared with the bare gold nanorod, the nanocomposite with the core-shell structure showed superior photothermal effect. The photothermal conversion temperature reached 63 °C under a lower irradiation power. The photothermal conversion efficiency was enhanced to 77.6%. Its photothermal performance remained constant after five cycles of near-infrared laser irradiation, indicating excellent photothermal stability. In vitro cell imaging experiments show that AuNRs@SiO2@ AuNCs can effectively enter tumor cells. By 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis, cancer cells can be effectively killed when exposed to a near-infrared laser. During the synthesis process, the silica and gold nanoclusters replaced the toxic CTAB molecular layer on the surface of AuNRs. Therefore, AuNRs@SiO2@AuNCs has good biocompatibility and fluorescence characteristics. These results suggest that such AuNRs@SiO2@AuNCs nanocomposite shows great potential in imaging guided photothermal therapy for cancer.

Highly fatigue-resistant photochromism of wool surface printed with spiropyran/chitosan microcapsules

A smart photochromic chitosan microcapsule, which was prepared by emulsification-chemical crosslinking technique utilizing spiropyran compound EDN as core material and chitosan as shell material, was printed onto wool fabric through screen-printing process. The photochromic microcapsule was adhered onto the surface of wool fabric via the adhering and crosslinking system. The microcapsule exhibited an approximately spherical shape with a size of 3∼4 μm, and could withstand high temperature around 300°C. The time of the color development and fading stability of the microcapsule dispersions were 4.25 s and 26.00 s, respectively, which were only 0.25 s and 4.00 s slower than that of the photochromic spiropyran dispersion, respectively. When the amount of microcapsule was 8wt% and the amount of adhesive DH-BS was 15wt%, the printed fabric had remarkable photochromic responsibility and good colorfastness. The printed wool fabric presented high fatigue resistance, and the K/S, L*, a* values of the printed wool fabric were nearly no change during 25 consecutive UV/Vis irradiation cycles.

Detailed Electrochemical Model of Microphotosynthetic Power Cells

A detailed and interdisciplinary explanation of the operation of microphotosynthetic cells ( μ -PSCs) from chemical reactions modeling to energy harvesting is provided in this article. The model includes the effect of photosynthesis and respiration of algae cells as well as the effect of irradiance, day and night cycle, temperature, and pH of the solution. It has an interdisciplinary explanation built on knowledge accumulated from different fields, such as chemical, biological, electrical sciences, and practical results. It covers the theory of the operation of μ -PSCs, the electrochemical model, the equivalent circuit representation of μ -PSCs, and energy harvesting from μ -PSCs. This article provides a simple but thorough insight into a better understanding and improvement of the μ -PSCs technology.

Optofluidic Photonic Crystal Fiber Microreactors for In Situ Studies of Carbon Nanodot-Driven Photoreduction.

Performing quantitative in situ spectroscopic analysis on minuscule sample volumes is a common difficulty in photochemistry. To address this challenge, we use a hollow-core photonic crystal fiber (HC-PCF) that guides light at the center of a microscale liquid channel and acts as an optofluidic microreactor with a reaction volume of less than 35 nL. The system was used to demonstrate in situ optical detection of photoreduction processes that are key components of many photocatalytic reaction schemes. The photoreduction of viologens (XV2+) to the radical XV•+ in a homogeneous mixture with carbon nanodot (CND) light absorbers is studied for a range of different carbon dots and viologens. Time-resolved absorption spectra, measured over several UV irradiation cycles, are interpreted with a quantitative kinetic model to determine photoreduction and photobleaching rate constants. The powerful combination of time-resolved, low-volume absorption spectroscopy and kinetic modeling highlights the potential of optofluidic microreactors as a highly sensitive, quantitative, and rapid screening platform for novel photocatalysts and flow chemistry in general.

GCT-70. INTRACRANIAL GROWING TERATOMA SYNDROME IN CHILDREN

Germ cell tumors account for less than 5% of all intracranial malignancies in children. Intracranial growing teratoma syndrome (GTS) is a rare pathophysiologic process characterized by growth of mature teratoma elements of a non-germinomatous germ cell tumor (NGGCT) during or following treatment with chemotherapy, in addition to normalization of or declining AFP/βHCG of the cerebral spinal fluid (CSF)/serum. A 13-year-old male presented with headache, emesis, and diplopia. MRI of the brain/spine revealed a localized 3.1 x 3.1 x 3.2 cm pineal tumor. Biopsy confirmed NGGCT (germinoma, immature and mature teratoma). Serum AFP (227ng/ul) and βHCG (12 IU/L) and CSF AFP (21ng/ul) and βHCG (31 IU/L) were elevated. Prior to cycle two of chemotherapy, he developed unstable gait and moderate hearing loss. Repeat MRI brain demonstrated tumor enlargement (4.4 x 5.2 x 5.1 cm) and obstructive hydrocephalus, although serum AFP/βHCG had normalized. Gross total resection of tumor confirmed GTS, without residual immature/malignant elements. Following six cycles of multiagent chemotherapy (carboplatin, etoposide, ifosfamide) and proton beam craniospinal irradiation (36 Gy with 18 Gy boost), he remains free of disease at eleven months since diagnosis. The pathogenesis of GTS remains unclear. Care must be taken to avoid misdiagnosing GTS as progressive NGGCT, as treatment and prognosis differ significantly. Second-look surgery, with a goal of complete resection, should be considered in cases of NGGCT when residual tumor grows during or following therapy, as this may represent GTS. Although histologically benign, GTS can be fatal. In patients with GTS, complete resection is usually curative.